NEW YORK -- The investment that the Yankees made in Masahiro Tanaka has so far proven to be worth its weight in yen.

Just when they needed it the most, the right-hander shut down the Mets, 4-0, on Wednesday night at Citi Field, giving the American League club its first win in a Subway Series game since 2012, and first in Queens since 2011.

It was a night of Major League Baseball firsts for Tanaka: first complete game, first shutout, first hit -- a ninth-inning single.

With the four-hitter, Tanaka ran his record as a Yankee to 6-0 and his ERA to 2.17. The Yankees, at 20-19, are five games under .500 sans Tanaka's contributions. Having helped the Yanks snap an overall four-game losing streak, Tanaka has thus far exceeded expectations.

"I think that's fair to say," Yankees manager Joe Girardi said. "I don't know that you expect anyone to go 6-0 to start out a season when you're a rookie and it's the first time you're on a schedule like this. He's special."

The Yankees won the Tanaka derby this past January by paying out a total of $175 million, $155 million to Tanaka for seven years, and an additional $20 million posting fee to his former Japanese club, the Rakuten Golden Eagles. Just to put the worth of that deal into perspective, it is larger than the full 2014 player payroll of 27 of Major League Baseball's 30 clubs.

Considering that it's back to the weaker links of their makeshift starting rotation, beginning with rookie Chase Whitley making his inaugural big league start on Thursday night against the Mets, the Yanks needed every bit of what Tanaka had to offer.

Under those circumstances, Girardi said that Tanaka has been "as valuable as anyone on our team."

But Girardi quickly added that it wasn't fair to place the onus on Tanaka to constantly stop the Yankees' bleeding.

"I have to manage him independently of everybody else, to make sure that he stays strong and he stays healthy," Girardi said. "If he'd been here a couple of years and he'd have been here the whole year, you might manage him a little bit differently. But given that it's the first time he's been in this type of situation, you can't put too much [pressure] on him."

Tanaka is everything he was billed to be. He hasn't lost a regular-season game on two continents since Aug. 19, 2012, and is 34-0 during that span, including a 24-0 mark last year for Rakuten, setting the Nippon Professional Baseball record for victories in a single season, plus leading the league with a 1.27 ERA.

Tanaka's 114-pitch outing on Wednesday night was his high-water mark for the Yanks. But consider that in last year's Japan Series victory over the Yomiuri Giants, Tanaka threw 160 pitches in a complete-game Game 6 loss, then came back in the ninth inning of Game 7 to record the save and lock down the Series.

Tanaka is following the legacy of some highly touted Japanese starters to the U.S., including Hideo Nomo, Daisuke Matsuzaka and Yu Darvish. Many a player would have come to the Major Leagues from across the Pacific trying to live up to the big contract, the expectations and all the hype, but not Tanaka.

"Being that this is my first season here, I don't think a lot of people were looking at me being a reliable front-end starting pitcher," Tanaka said through a translator. "I think that it's too early to say I'm successful here. Obviously, I have a seven-year contract, and it's important for me to be successful throughout those years. So I'm just taking it day by day and trying to become a better pitcher."

So far, so good. Making his eighth start, Tanaka walked none and struck out eight Wednesday. In his first 58 innings, he has a 7-to-66 walk-to-strikeout ratio. Along the way, Tanaka has given up only 14 earned runs and 46 hits, seven home runs.

Comparatively, Yankees starters are ranked 23rd in the big leagues and 10th in the AL with a 4.24 ERA, a full 2.07 higher than the one sported right now by Tanaka. That's how much impact he has had on the starting staff.

The 25-year-old has a beaming smile and an affable demeanor, easily and cooperatively answering sets of questions from the English and Japanese media.

If there was any thought of Tanaka having a problem making the transition to the Major Leagues, that hasn't come to pass. He's as fluid in his personality as he is with his motion, throwing five pitches of different speeds and rotation.

Mets manager Terry Collins, who saw Tanaka firsthand when he managed for two seasons in Japan, said it's no secret why he has been so successful.

"You saw it tonight," Collins said. "Everything is a strike. He's around the dish. He throws all his pitches. He's never in a count where you can look for something. He got some strikeouts tonight, but I've seen his splitter where it's so effective you can't hit it. When you're ahead like he is and you're around the plate like he is, you've got to be ready to swing. That's why he's great."

To punctuate that point, Mets second baseman Daniel Murphy added about his 1-for-4 in the game: "I knew what was coming, but I just couldn't hit it."

The Yankees, of course, will take it. The Mets had scored 21 runs in winning the first two games of the series this week in the Bronx. All too often, opposing hitters have known what was coming from Yanks pitchers and could hit it.

Tanaka, though, was his usual dominant self on Wednesday night, and for the Yankees, that made all the difference.